1. Field of the Invention
The present invention relates generally to a fluid sampling device which may be used to obtain, for example, ground water samples from a well. More particularly, the invention relates to a combination two-stage pump device which includes both a reciprocating (piston) pump for purging water prior to sampling, and a bladder pump for withdrawing actual samples.
2. Description of the Relevant Art
Ground water contamination has become a primary area of environmental concern, resulting in a disideratum for efficient equipment for withdrawing water samples from monitoring wells so that it may be chemically analyzed. Such sampling equipment must not only comply with governmental restrictions; it should also be time, energy and cost efficient.
One set of conflicting demands which arises is that whereas governmental restrictions require that a bladder-type pump be used to obtain the most representative well water sample for analysis, this type of pump is highly inefficient for necessary initial purging operations due to its relatively slow pumping speed.
Prior arrangements have relied upon the use of both a bladder pump for obtaining samples; and a second pump, such as an air lift pump, for initial purging operations. Such arrangements require separate mounting of the bladder and air lift pumps, which results in increased costs for producing and controlling the two pumps separately. In the case where two such pumps are mounted side-by-side in a well casing, the diameter of the associated well casing must be large enough to accommodate same. Further, separate provisions must in any case be made for extending the lengths of the fittings for each pump when the monitoring well is very deep.
In applicant's prior U.S. Pat. No. 4,701,107 filed Apr. 4, 1986, there is disclosed a two-stage pump sampler device which fulfills the above-described desideratum by combining an air lift and bladder pump into a two-stage single pumpd. The two pumps are coaxially arranged in a single casing to permit independent initial purging by the air lift pump, and subsequent water sampling by the bladder pump.
It is an object of the present invention to provide a novel two-stage pump sampler device which also fulfills the aforesaid desideratum, and which does so by combining a reciprocating (piston) pump and a bladder pump in a single coaxial arrangement. The two pumps are independently operable to permit efficient initial purging by the piston pump, and subsequent representative water sampling by the bladder pump.
The two-stage pump sampler device according to the present invention also eliminates any need for vacuum in the bladder pump operation, and prevents the water sample from being exposed to negative pressure or air.
By virtue of its novel two-stage pump arrangement, the device according to the present invention may be employed in relatively small-diameter well casings in comparison with other known samplers, is readily extensible to accommodate various well depths, and is relatively simple and inexpensive to manufacture.